Walkin has a career high ATP doubles ranking of 204, achieved on June 19, 2023, and a career high singles ranking of 702 achieved on 17 February 2020[1] Walkin made his ATP main draw debut at the 2022 Adelaide International 2 after receiving a wildcard into the doubles main draw with Harry Bourchier.

In 2014 and 2015 Walkin played on the ITF in Australia and Europe, with the second round being he best performance in singles and semi-finals in doubles.

In May 2019, Walkin reached his first singles ITF final in M15 Cancun, which saw him re enter the ATP top 1000 rankings.

Walkin also competed in the Australian Open Wildcard Playoffs in 2019 losing to eventual winner J.P Smith Walkin started 2020 playing in the North American ITF Circuit, achieving a semi-final run at Cancun, Mexico, before the COVID-19 pandemic stopped play in March 2020.

Walkin made his ATP Tour debut at the 2022 Adelaide International 2, playing doubles alongside Harry Bourchier.